This patchset implements BPF_LWT_ENCAP_IP mode in bpf_lwt_push_encap BPF helper. It enables BPF programs (specifically, BPF_PROG_TYPE_LWT_IN and BPF_PROG_TYPE_LWT_XMIT prog types) to add IP encapsulation headers to packets (e.g. IP/GRE, GUE, IPIP).
This is useful when thousands of different short-lived flows should be encapped, each with different and dynamically determined destination. Although lwtunnels can be used in some of these scenarios, the ability to dynamically generate encap headers adds more flexibility, e.g. when routing depends on the state of the host (reflected in global bpf maps). V2 changes: Added flowi-based route lookup, IPv6 encapping, and encapping on ingress. V3 changes: incorporated David Ahern's suggestions: - added l3mdev check/oif (patch 2) - sync bpf.h from include/uapi into tools/include/uapi - selftest tweaks V4 changes: moved route lookup/dst change from bpf_push_ip_encap to when BPF_LWT_REROUTE is handled, as suggested by David Ahern. V5 changes: added a check in lwt_xmit that skb->protocol stays the same if the skb is to be passed back to the stack (ret == BPF_OK). Again, suggested by David Ahern. V6 changes: reject skb_is_gso() packets. A follow-up patch(set) will process GSO packets more intelligently. Peter Oskolkov (5): bpf: add plumbing for BPF_LWT_ENCAP_IP in bpf_lwt_push_encap bpf: implement BPF_LWT_ENCAP_IP mode in bpf_lwt_push_encap bpf: add handling of BPF_LWT_REROUTE to lwt_bpf.c bpf: sync <kdir>/<uapi>/bpf.h with tools/<uapi>/bpf.h selftests: bpf: add test_lwt_ip_encap selftest include/net/lwtunnel.h | 3 + include/uapi/linux/bpf.h | 23 +- net/core/filter.c | 47 ++- net/core/lwt_bpf.c | 188 +++++++++++ tools/include/uapi/linux/bpf.h | 23 +- tools/testing/selftests/bpf/Makefile | 5 +- .../testing/selftests/bpf/test_lwt_ip_encap.c | 85 +++++ .../selftests/bpf/test_lwt_ip_encap.sh | 311 ++++++++++++++++++ 8 files changed, 674 insertions(+), 11 deletions(-) create mode 100644 tools/testing/selftests/bpf/test_lwt_ip_encap.c create mode 100755 tools/testing/selftests/bpf/test_lwt_ip_encap.sh -- 2.20.1.611.gfbb209baf1-goog
